Search lights are extensively used on police and rescue helicopters to illuminate subjects on the ground and in the water. Generally, search lights are mounted on gimbles which enable the search lights to be angularly adjusted with respect to helicopters in order for the light beams of the search lights to remain in alignment with subjects under scrutiny. This is necessary because a subject may move with respect to a helicopter, either as the helicopter moves, or when the helicopter is substantially stationary and the subject moves. It is frequently necessary to first illuminate a relatively large area in order to locate whatever subject is of interest and then to progressively illuminate smaller and smaller areas in order to isolate the subject so that the subject can be readily discernable by a helicopter crew or other observers either on the ground or at another location.
Currently, the focus of a search light beam from a helicopter mounted search light is adjusted by a uni-directional cam which is driven to rotate in only one direction by a DC motor. Consequently, if a desired focus angle has been passed and one wishes to change the size of an area illuminated, there is a lag period as the uni-directional cam recycles. This can result in the subject being observed either escaping from or unintentionally moving out of an illuminated area. It is therefore desirable to rotate the cam in both directions in order to enhance an operator's ability to maintain a desired illuminated area or to rapidly change the size of the area without recycling the cam.
In helicopters and fixed-wing aircraft, search lights are generally connected by a connecting wire harness to internal cable systems within the fuselage of the helicopter or aircraft. In accordance with standard practice, there is only a single wire in the connecting wire harness devoted to interfacing with the focus control for the search lights, which focus control axially moves bidirectionally according to the rotational position of the uni-directional cam. Normally in order to make the cam bidirectional, the DC motor must run in both directions. In the prior art bidirectional motor rotation requires two wires, one for each direction of cam rotation. In order to provide a second wire in the wire harness, the wire harness must be changed or re-engineered. Moreover, after the wire harness has been changed or re-engineered, the helicopter or aircraft must be inspected by licensing authorities and the new wiring arrangement approved before the aircraft or helicopter is legally allowed to fly. This is an expensive, time-consuming undertaking which requires not only re-wiring of the connecting harness but also re-wiling of the search lights and search light controls. Consequently, helicopters and aircraft already equipped with search lights having a single wire for focus control forego improvements in focus control which would enable focus control to proceed in both directions rather than a single direction.
In view of the aforementioned considerations, there is a need for an arrangement which allows a search light on a helicopter or an aircraft to be modified in order to have a bidirectional focus control without having to do any re-wiring.
While this problem is primarily a problem with search lights mounted on platforms such as helicopters and fixed wing aircraft, it is also a consideration for other platforms such as search lights mounted on boats and land vehicles and even those mounted on remotely controlled stationary supports.